Cardiac Cycle

• Heart and Cardiac Cycle

  1. Four chambers - right and left atria, right and left ventricles

  2. Four main blood vessels - pulmonary vein (from lungs to left atrium), aorta (from left ventricle to body), vena cava (from body to right ventricle), pulmonary artery (from right atrium to lungs)

  3. Atrioventricular valves - separate atria from ventricles

  4. Semilunar valves -separate arteries from ventricles

  6. Coronary arteries - wrapped around the heart to supply blood to cardiac muscle

  7. Cardiac muscle - thicker on the left-hand side because higher pressure is needed to pump blood round the body
• Cardiac diastole


  Atria and ventricles relax, pressure inside the heart chambers decreases, causing semilunar valves in the aorta and pulmonary arteries to close, preventing backflow of blood
• Closing atrioventricular valves and opening semilunar valves

  Allows blood to leave the left ventricle through the aorta and right ventricle through the pulmonary artery
• Cardiac diastole


  The phase in the cardiac cycle following ventricular systole where the atria and ventricles are both relaxed and blood flows into the atria
• Atrial systole


  The phase in the cardiac cycle following diastole where the atria contract and force the blood into the ventricles
• Ventricular systole

  The phase in the cardiac cycle following atrial systole where the ventricles contract and force the blood out of the heart and around the body
• 3 stages of the cardiac cycle

  Atrial systole - during atrial systole the atria contract forcing the atrioventricular valves open and blood flows into the ventricles.

  Ventricular systole - contraction of the ventricles causes the atrioventricular valves to close and semilunar valves to open thus allowing blood to leave the left ventricle through the aorta and right ventricle through the pulmonary artery.

  Cardiac diastole - atria and ventricles relax and pressure inside the heart chambers decreases causing semilunar valves in the aorta and pulmonary artery to close.